Scientists Find Common Molecular Pathways Between Rett Syndrome and Schizophrenia

Gene mutations that cause a severe childhood neurological disorder called Rett Syndrome have now also been implicated in childhood-onset schizophrenia. Dr. Huda Zoghbi, a Rett Syndrome Research Trust Scientific Advisor, published her recent research in the November issue of the journal Nature.

MECP2 and GABA Link the Two Neurological Conditions

Rett syndrome is a rare and severe form of autism that predominantly strikes girls with the first symptoms appearing before the age of 18 months. Children with Rett syndrome have increasing problems with movement, coordination and communication. It affects 1 in every 10,000 children. Most live to become adults who require total, around-the-clock care.

Rett syndrome appears to be caused by a mutation in the MECP2, a gene essential for the normal function of nerve cells. The gene is located on the X chromosome, which explains why the condition is seen primarily in girls who have two X chromosomes versus boys who only have one.

Dr. Zoghbi first discovered the association between MECP2 and Rett syndrome using a mouse model. She removed MECP2 from every cell and found that it resulted in full-blown symptoms that accurately represented the range of symptoms seen in humans. Digging deeper, she discovered that removing the gene appears to reduce the production of a brain neurotransmitter called GABA, or gamma amino butyric acid, by about 30% which appeared to be the primary cause of the increased symptoms.

GABA is the main inhibitory neurotransmitter in the brain. Neurons releasing GABA regulate the nervous system by modulating the brain’s “information highway”, allowing for a balanced level of neuronal activity.

GABA is also implicated in the pathogenesis of schizophrenia. Authors from the University of Texas Health Sciences Center in 2003 published an analysis of literature in the Journal of Clinical Psychopharmacology which suggests that alterations in the GABA neurotransmitter system affects both receptors and reuptake sites in patients and may affect other brain chemicals involved in the disorder, such as dopamine.

The authors suggest that boosting the activity of GABA-producing neurons may help to alleviate the severity of some symptoms in many neuropsychiatric disorders.

"This study revealed to us the critical role of MECP2 in modulating the levels of GABA in inhibitory neurons and pinpointed all the neuropsychiatric symptoms that develop when the function of inhibitory neurons is compromised. Identifying the cellular and chemical basis of such symptoms is a first step in efforts aimed at understanding and, one day, treating such disorders," said Zoghbi.